Energy return sole for footwear

Abstract

An article of footwear having an upper, an outsole defining a ground engaging surface, and a sole disposed between the upper and the outsole. The sole includes an energy return system having a first rigid plate, a second rigid plate spaced a predetermined distance from the first rigid plate, and at least one separating element disposed therebetween to maintain the spacing between the plates.

1. An article of footwear comprising:
 an upper;  
 a sole having a ground engaging portion and an energy return system between the upper and the sole;  
 the energy return system comprising: 
 an upper plate and a lower plate spaced a predetermined distance from each other, the upper and lower plates having heel, arch, and toe portions, respectively, and made from an elastic material of high tensile strength, the plates independently deformable and recoverable from heel portion to toe portion; and  
 two elastomeric elements, one disposed between the toe portion of the plates and the other disposed between the heel portion of the plates to maintain the spacing between said plates during a gait cycle of a wearer comprising a heel strike, a midstance, and a toe off;  
 
 during heel strike the heel portion of the upper plate deforms downward and the arch portion of the upper plate deforms upward;  
 during midstance the arch portion of both the upper and lower plates deforms downward and the heel portion of the upper plate recovers to a non-deformable state rocking the wearer forward; and  
 during toe off the upper and lower plates recovers to the non-deformable state releasing stored energy into a step forward and upward propelling the wearer forward.  
 
   
   
     2. The article of footwear of  claim 1 , wherein the upper plate has a lateral side and a medial side, and wherein during heel strike the heel portion of the upper plate has greater deformation on the lateral side than the medial side. 
   
   
     3. The article of footwear of  claim 2 , wherein during midstance the arch portion of the upper plate has greater deformation on the lateral side than the medial side. 
   
   
     4. The article of footwear of  claim 3 , wherein during toe off the deformation of the toe portion of the upper plate shifts from the lateral side to the medial side. 
   
   
     5. The article of footwear of  claim 1 , wherein one of the two elastomeric elements is positioned at a posterior end of the upper and lower plates. 
   
   
     6. The article of footwear of  claim 1 , wherein said upper and lower plates comprise a material having a modulus of elasticity of at least approximately 32×10 6  lb/in 2 . 
   
   
     7. The article of footwear of  claim 6 , wherein said material comprises carbon graphite. 
   
   
     8. The article of footwear of  claim 7 , wherein said upper plate and lower plates are formed by a plurality of layers of carbon graphite. 
   
   
     9. The article of footwear of  claim 1 , wherein said first one of said separating elements is generally arcuate. 
   
   
     10. The article of footwear of  claim 1 , wherein one of the separating elements is located entirely forward of a ball of a wearer's foot. 
   
   
     11. The article of footwear of  claim 1 , wherein the toe portion of the upper plate deflects downward before the upper and lower plates return to the non-deformable state. 
   
   
     12. An energy return system for use in a shoe sole comprising:
 an upper plate and a lower plate spaced a predetermined distance from each other, the upper and lower plates having heel, arch, and toe portions, respectively and made from an elastic material of high tensile strength, the plates independently deformable and recoverable from heel portion to toe portion;  
 two elastomeric elements, one disposed between the toe portion of the plates and the other disposed between the heel portion of the plates to maintain the spacing between said plates during a gait cycle of a wearer comprising a heel strike, a midstance, and a toe off wherein;  
 during heel strike the heel portion of the upper plate deforms downward and the arch portion of the upper plate deforms upward;  
 during midstance the arch portion of both the upper and lower plates deforms downward and the heel portion of the upper plate recovers to a non-deformable state rocking the wearer forward; and  
 during toe off the upper and lower plates deforms to the non-deformable state releasing stored energy into a step forward and upward propelling the wearer forward.  
 
   
   
     13. The article of footwear of  claim 12 , wherein the upper plate has a lateral side and a medial side, and wherein during heel strike the heel portion of the upper plate has greater deformation on a lateral side than a medial side. 
   
   
     14. The article of footwear of  claim 13 , wherein during midstance the arch portion of the upper plate has greater deformation on the lateral side than the medial side. 
   
   
     15. The article of footwear of  claim 14 , wherein during toe off the deformation of the toe portion of the upper plate shifts from the lateral side to the medial side. 
   
   
     16. The article of footwear of  claim 12 , wherein one of the two elastomeric elements is positioned at a posterior end of the upper and lower plates. 
   
   
     17. The energy return system of  claim 12 , wherein said upper and lower plates comprise a material having a modulus of elasticity of at least approximately 32×106 lb/in 2 . 
   
   
     18. The energy return system of  claim 17 , wherein said material comprises carbon graphite. 
   
   
     19. The energy return system of  claim 18 , wherein said upper plate and lower plates are formed by a plurality of layers of carbon graphite. 
   
   
     20. The energy return system of  claim 12 , wherein said first one of said separating elements is generally arcuate. 
   
   
     21. The energy return system of  claim 12 , wherein one of the separating elements is located entirely forward of a ball of a wearer's foot. 
   
   
     22. The energy return system of  claim 12 , wherein the toe portion of the upper plate deflects downward before the upper and lower plates return to the non-deformable state.